ELEMENT DEFINISSANT UNE FENTE, A MONTER SUR UN ARBRE

ELEMENT THAT DEFINES A GAP AND IS TO BE MOUNTED ON A SHAFT

Abrégé français

L'invention concerne un élément définissant une fente pour le passage limité d'un milieu d'écoulement, à monter sur l'arbre d'une turbomachine. Ledit élément comprend une partie de type douille (2) à monter sur l'arbre de la turbomachine, qui présente une cavité (4) pour une bague (5) au niveau de sa périphérie extérieure. La bague (5) dont les faces d'about sont en partie entourées de parois en anneau de cercle de la cavité (4) lorsque la turbomachine est en service, a) forme, conjointement avec les parois en anneau de cercle de la cavité (4), dans chaque cas une fente axiale et une fente radiale, avec le fond de la cavité ; b) la bague est maintenue par une paroi rigide (1) entourant ladite bague, par liaison de friction. L'invention vise à réduire l'usure des bagues consistant en un matériau souple coulant. A cet effet, il est prévu selon l'invention de former un évidement dans la paroi rigide (1), qui entoure les faces d'about libre de la bague (5), dégagées des parois de la partie de type douille. Une des délimitations latérales de l'évidement (4) est formée par un élément tubulaire (7) relié de manière amovible à la paroi rigide (1).

Abrégé anglais

The invention relates to an element, which is to be mounted on the shaft of a
non-positive--displacement
machine and which forms a gap for the limited passage of a flowing medium.
Said
element comprises a bush-like part (2), which is to be mounted on the shaft of
the non-positive--displacement
machine and whose outer periphery is provided with a recess (4) for
accommodating a ring (5). During operation of the non-positive-displacement
machine, the ring
(5), which is partially surrounded on its faces by circular ring-shaped walls
of the recess (4); a)
forms an axial gap with the circular ring-shaped walls of the recess (4) and
forms a radial gap
with the bottom of the recess, and; b) is held via frictional contact by a
rigid wall (1) surrounding
the ring (5). In order to reduce wear to the rings made of a soft flowable
material, the invention
provides that a recess is formed in the rigid wall (1) and surrounds the faces
of the ring (5) that
are free from the walls of the bush-like part. One of the lateral
delimitations of the recess (4) is
formed by a tubular part (7) detachably joined to the rigid wall (1).

Revendications

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CLAIMS:
1. An assembly for mounting on a shaft of a
non-positive displacement machine, said assembly comprising:
a piston for mounting on the shaft of the machine,
said piston having an outer periphery provided with a first
recess,
a piston ring comprising a soft, flowable material
and accommodated in said first recess and having end faces
which are partially surrounded by circularly annular walls
of said first recess, and
an annular bush defining a rigid wall surrounding
the piston ring and provided with a second recess,
wherein said piston ring a) forms with each
circularly annular wall of the first recess an axial gap
that extends in full-length from the bottom of the first
recess to the end of each circularly annular wall of the
first recess and forms a radial gap with the bottom of the
first recess that extends in full-length from one side of
the first recess to the other and wherein the radial gap
connects the axial gaps to form a continuous gap, and b) is
held by contact with said rigid wall surrounding the piston
ring,
wherein the second recess encloses the end faces
of the piston ring that extend beyond the circularly annular
walls of the first recess, and
wherein said second recess is also partly defined
by a tubular part detachably joined to the rigid wall.
2. An assembly according to claim 1, wherein the one
of the walls of said first recess is located opposite said

-7-
tubular part and is formed by a holding ring which is
detachably joined to the annular bush.
3. An assembly according to claim 2, wherein said
piston ring is a closed ring inserted with a frictional fit
into said annular bush, and wherein the rigid wall surrounds
the closed ring.
4. An assembly according to claim 1, wherein the
piston ring is a resilient ring which is separated by a
longitudinally extending gap and can be pushed over a
lateral wall of the piston by being expanded and then
secured in the first recess, and wherein the contact between
the piston ring and the rigid wall arises through expansion
which occurs during operation of the non-positive
displacement machine.
5. An assembly according to claim 1, wherein the
annular bush is fastenable in a housing of the non-positive
displacement machine in a rotationally fixed and
nondisplaceable manner.
6. An assembly according to claim 1, wherein said
assembly defines a cartridge adapted for assembly outside
the non-positive displacement machine that is installable in
the machine as a unit.
7. An assembly according to claim 1, wherein said
assembly is an axial thrust balancing device.
8. An assembly according to claim 1, wherein said
assembly is a shaft seal.

Description

CA 02498633 2005-03-10
WO 2004/036053 PCT/EP2003/009503
KSB Aktiengesellschaft
Description
Element that defines a gap and is to be mounted on a
shaft
The subject matter of the invention is an element which
is to be mounted on the shaft of a non-positive
displacement machine and which forms a gap for the
limited passage of a flowing medium, having a bush-like
part which is to be mounted on the shaft of the non-
positive displacement machine and whose outer periphery
has a recess for a ring, the ring which is partially
surrounded at its end faces by circularly annular walls
of the recess during operation of the non-positive
displacement machine
a) forming an axial gap in each case with the
circularly annular walls of the recess and forming
a radial gap with the bottom of the recess,
b) being held via frictional contact by a rigid wall
surrounding the ring.
An element of this type has already been used in the
subject matters of DE 100 38 586 Al and DE 100 62 204
Al. There, it served as a relief piston in an axial
thrust balancing device or as a sealing bush in a shaft
seal. A common feature of both applications was that a
slotted resilient ring was used which was widened
slightly during operation of the non-positive
displacement machine by the prevailing pressure,
pressed against the housing inner wall and fixed in
such a way. However, the invention is not aimed only
at elements with slotted rings, but is intended also to

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be suitable for application in closed rings. Independently
of the design, rings made from a soft, flowable material
result in the problem that their edge zones on the one side
are pressed gradually into the gap between the piston or
bush attached to the shaft and the surrounding housing hole
by the pressure which acts on them. This results in
increasing wear of the ring and the risk of the sealing
action diminishing.
It is an object of an embodiment of the invention
to avoid the mentioned wear and thus to increase the service
life of the ring and therefore also of the element which is
described in the introduction.
According to the invention, a recess is formed in
the rigid wall surrounding the ring and surrounds the end
faces of the ring that are free from the walls of the bush-
like part, one of the lateral delimitations of the recess
being formed by a tubular part detachably joined to the
rigid wall.
According to an aspect of the invention, there is
provided an assembly for mounting on a shaft of a non-positive
displacement machine, said assembly comprising: a piston for
mounting on the shaft of the machine, said piston having an
outer periphery provided with a first recess, a piston ring
comprising a soft, flowable material and accommodated in said
first recess and having end faces which are partially
surrounded by circularly annular walls of said first recess,
and an annular bush defining a rigid wall surrounding the
piston ring and provided with a second recess, wherein said
piston ring a) forms with each circularly annular wall of the
first recess an axial gap that extends in full-length from the
bottom of the first recess to the end of each circularly
annular wall of the first recess and forms a

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radial gap with the bottom of the first recess that extends
in full-length from one side of the first recess to the
other and wherein the radial gap connects the axial gaps to
form a continuous gap, and b) is held by contact with said
rigid wall surrounding the piston ring, wherein the second
recess encloses the end faces of the piston ring that extend
beyond the circularly annular walls of the first recess, and
wherein said second recess is also partly defined by a
tubular part detachably joined to the rigid wall.
As a result of the design according to the
invention, the ring is surrounded on all sides; no gap into
which the ring could yield therefore remains.
In order for it to be possible to move a closed
ring into its position within the piston or the shaft-side
bush, a delimitation ring which is detachably joined to the
piston or the bush is arranged in that wall of the recess of
said part which lies opposite the tubular part. It goes
without saying that it is also possible in this way to mount
a resilient ring which is separated by a longitudinally
running gap. However,

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with less expenditure for the shaft-side bush-like
part, this can also be widened and pushed over one of
the lateral walls of the bush-like part.
A particular advantage of the invention consists in
that the entire element, including the surrounding wall
which in this case is likewise formed by a bush, can be
combined outside the non-positive displacement machine
from separately manufactured parts to form a cartridge
which is ready for installation.
Above all, the invention is to be used advantageously
as an axial thrust balancing device or as a shaft seal.
The invention will be explained in greater detail using
two exemplary embodiments. In the drawing:
fig. 1 shows a sectional illustration of an element
which is configured as a cartridge which can be
installed, having a resilient ring which is
divided in the axial direction by a slot; and
fig. 2 shows a sectional illustration of a cartridge
which corresponds largely to fig. 1, having a
closed ring.
The cartridges which are shown in figs. 1 and 2 serve
as relief pistons in axial thrust balancing devices. A
common feature of both refinements is a bush 1 which is
to be mounted in a rotationally fixed and
nondisplaceable manner in a centrifugal pump housing
(not shown). The remaining parts of the elements are
inserted in each case into the bush 1. A further bush-

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like element, a piston 2 or 3, is to be arranged on the
shaft (not shown) of the centrifugal pump.
In the refinement according to fig. 1, the piston 2 has
a recess 4 into which a piston ring 5 is inserted. The
piston ring 5 consists of resilient material and is
separated by an axially running slot (not shown) . The
resilience and the separation make it possible for the
piston ring 5 to be pushed over the side wall 6 of the
piston and to be latched into the recess 4. Provided
on that side of the cartridge which lies opposite the
side wall 6 is a tubular holding ring 7 which is
inserted into the bush 1 after introduction of the
piston 2 and of the piston ring 5 and is fastened to
the bush 1 by screws 8. The holding ring 7 has two
effects: Firstly, the cartridge is held together by it.
Secondly, it prevents the piston ring 5 from expanding
into the region between the piston 1 and the bush 2, as
a result of which gradual wear is avoided in the region
of an existing gap in the previously known
configuration.
In the refinement according to fig. 2, the piston 3 has
a shoulder 9 onto which a closed piston ring 10 is
pushed. In order to form a complete recess in which
the piston ring is held, a delimitation ring 12 which
is fastened to the piston 3 by means of screws 11 is
attached on the open side of the piston 3, that is to
say opposite the holding ring 7. The holding ring 7
and the screws 8 correspond to the refinement of
fig. 1.
A modification results if, instead of a cartridge which
is ready for installation, a bush is used which is

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fastened in the housing of the non-positive
displacement machine and is connected to the other
parts of the element only in the housing. The
invention is nevertheless also used in a refinement of
this type which appears less advantageous.
Although it serves a different purpose, the
construction of an element for sealing a shaft is in
principle the same as in the relief devices explained
here. However, the corresponding parts are denoted
there by other designations than in the exemplary
embodiments presented here.

Dessin représentatif